1. Field of the Invention
A voice activity detector is a device which is supplied with a signal with the object of detecting periods of speech, or periods containing only noise. Although the present invention is not limited thereto, one application of particular interest for such detectors is in mobile radio telephone systems where the knowledge as to the presence or otherwise of speech can be exploited to reduce power consumption and interference by turning off a transmitter during periods of silence. Here also the noise level (from a vehicle-mounted unit) is likely to be high. Another possible use in radio systems is to improve the efficient utilisation of radio spectrum.
2. Related Art
FIG. 1 shows a voice activity detector as described in our International Patent Application WO89/08910.